| With the continuous extension and improvement of the high-speed railway network in the southeast coastal areas of China,in order to maximize the use of limited land resources,the phenomenon of loading near the existing high-speed railway bridges for subgrade filling is becoming more and more common.Large scale surcharge will lead to deformation of nearby soil mass,which will bring certain hidden dangers to the traffic safety of existing high-speed railway bridges.In addition to considering the influence of the construction process on the high-speed railway bridge,it is necessary to deeply study the influence of the consolidation of soft soil over time on the bridge after the completion of construction.In this thesis,the time-varying effect of loading on the pier displacement of the existing high-speed railway under the consolidation of soft soil is studied under the background of a new road on the soft soil and the existing continuous girder bridge of Shanghai-Nanjing and Hangzhou high-speed railway.The main contents of this thesis are as follows:(1)Two elastoplastic constitutive models,Mohr Coulomb and modified Cambridge,are analyzed and compared,and the appropriate constitutive model is selected according to the actual situation of soil layer.Based on the practical engineering background and ABAQUS software,a three-dimensional finite element model of Soil Bridge Track integration considering the consolidation effect of soft soil with time is established,and the rationality of the model is verified.(2)Based on the established three-dimensional finite element model,the single factor sensitivity analysis of soil parameters is carried out by using the perturbation method.The results show that the most sensitive factor is the Poisson’s ratio of muddy clay layer.When reduced by 1%,the disturbance amplitude to the lateral and vertical displacement of the pier before consolidation is 2.22% and 0.61% respectively;The disturbance amplitude to the lateral and vertical displacement of the pier after consolidation is basically stable is 6.35% and 0.79% respectively;In addition,the Poisson’s ratio of silty clay layer,the slope of rebound curve of soft soil layer,the critical state slope m and the cap curvature constant have a relatively large impact on the pier displacement.(3)The BBD test design method is used to fit the response surface function of the lateral and vertical displacement of the pier before soil consolidation and the time-varying response surface function of the lateral and vertical displacement of the pier during soil consolidation,and its reliability is verified;The three-dimensional curved surface diagram of pier displacement variation under the action of only two soft soil parameters is analyzed;The accuracy test of response surface function shows that the reliability of the fitted function is high,and the R2 of the regression model is between 0.95～1,and the RMSE value is close to 0,so the accuracy is high.(4)The parameters of soft soil layer were sampled for 107 times randomly,and the reliability probability of the lateral and vertical displacement values of the existing pier caused by the new parallel road at different times of soil consolidation within 1mm,2mm and 3mm was obtained.The results show that the reliable probability of the influence of the new road construction on the vertical displacement of the pier is high,and the vertical displacement basically remains between 1mm～2mm with the consolidation of the soil;The reliability probability of lateral displacement is low,and the lateral displacement will decrease with the consolidation of soil.With 28 graphs,35 sheets and 77 references. |
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